Somatic hypermutation and affinity maturation analysis using the 4-hydroxy-3-nitrophenyl-acetyl (NP) system

Somatic hypermutation of immunoglobulin variable region (IgV) genes and affinity maturation of the antibody response are the hallmarks of the germinal center (GC) reaction in T cell-dependent immune responses. Determining the consequences of the experimental manipulation of the GC response on somatic hypermutation and affinity maturation requires the availability of a system that allows measuring these parameters. Immunization of mice of the C57/Bl6 genetic background with the hapten 4-hydroxy-3-nitrophenyl-acetyl (NP) coupled to a carrier protein leads to the predominant usage of one particular IgV heavy chain gene segment, V186.2, among the responding B cells. Moreover, a specific somatic mutation in codon 33 of V186.2 that leads to a tryptophan to leucine amino acid exchange increases the affinity of the corresponding antibody by ~10-fold, thus representing a molecular marker for affinity maturation. In addition, due to the simplicity of the antigen and the virtual absence of NP-specific plasma cells prior to immunization, NP-based immunizations represent ideal tools to quantify the plasma cell response by measuring NP-specific antisera by ELISA and the generation of NP-specific plasma cells by ELISPOT analysis. We here describe approaches to (1) measure the anti-NP plasma cell response by ELISA and ELISPOT analysis, and to (2) amplify and sequence V186.2 rearrangements from GC B cells and plasma cells to determine the level of somatic hypermutation and the extent of affinity maturation in the anti-NP response

Germinal center B cells recognize antigen through a specialized immune synapse architecture

B cell activation is regulated by B cell antigen receptor (BCR) signaling and antigen internalization in immune synapses. Using large-scale imaging across B cell subsets, we show that in contrast to naive and memory B cells, which gathered antigen towards the synapse center before internalization, germinal center (GC) B cells extracted antigen by a distinct pathway using small peripheral clusters. Both naive and GC B cell synapses required proximal BCR signaling, but GC cells signaled less through the protein kinase C-β (PKC-β)–NF-κB pathway and produced stronger tugging forces on the BCR, thereby more stringently regulating antigen binding. Consequently, GC B cells extracted antigen with better affinity discrimination than naive B cells, suggesting that specialized biomechanical patterns in B cell synapses regulate T-cell dependent selection of high-affinity B cells in GCs

Mortalidade infantil e acesso geográfico ao parto nos municípios brasileiros

OBJETIVO: Analisar o acesso geográfico ao parto hospitalar nos municípios brasileiros. MÉTODOS: Foram analisadas informações de óbitos e nascimentos quanto à sua adequação para o cálculo do coeficiente de mortalidade infantil no período de 2005 a 2007 para os 5.564 municípios brasileiros. O acesso geográfico foi expresso por indicadores de deslocamento, oferta e acesso aos serviços de saúde. A associação entre o acesso geográfico ao parto e o coeficiente de mortalidade infantil em municípios com adequação de suas informações vitais foi avaliada por meio de regressão múltipla. RESULTADOS: Dentre os municípios analisados, 56% apresentaram adequação das informações vitais, correspondendo a 72% da população brasileira. O deslocamento geográfico ao parto mostrou-se inversamente associado ao porte populacional, à renda per capita, e à mortalidade infantil, mesmo controlado por fatores demográficos e socioeconômicos. CONCLUSÕES: Embora tenham sido desenvolvidas estratégias importantes para a melhoria da qualidade do atendimento às gestantes no Brasil, as ações para garantir o acesso igualitário à assistência ao parto ainda são insuficientes. O maior deslocamento intermunicipal para o parto se mostrou como um fator de risco para a mortalidade infantil, aliado à desigualdade de oferta de serviços qualificados e à falta de integração com a atenção básica de saúde

Contextual and individual assessment of dental pain period prevalence in adolescents: a multilevel approach

<p>Abstract</p> <p>Background</p> <p>Despite evidence that health and disease occur in social contexts, the vast majority of studies addressing dental pain exclusively assessed information gathered at individual level.</p> <p>Objectives</p> <p>To assess the association between dental pain and contextual and individual characteristics in Brazilian adolescents. In addition, we aimed to test whether contextual Human Development Index is independently associated with dental pain after adjusting for individual level variables of socio-demographics and dental characteristics.</p> <p>Methods</p> <p>The study used data from an oral health survey carried out in São Paulo, Brazil, which included dental pain, dental exams, individual socioeconomic and demographic conditions, and Human Development Index at area level of 4,249 12-year-old and 1,566 15-year-old schoolchildren. The Poisson multilevel analysis was performed.</p> <p>Results</p> <p>Dental pain was found among 25.6% (95%CI = 24.5-26.7) of the adolescents and was 33% less prevalent among those living in more developed areas of the city than among those living in less developed areas. Girls, blacks, those whose parents earn low income and have low schooling, those studying at public schools, and those with dental treatment needs presented higher dental-pain prevalence than their counterparts. Area HDI remained associated with dental pain after adjusting for individual level variables of socio demographic and dental characteristics.</p> <p>Conclusions</p> <p>Girls, students whose parents have low schooling, those with low <it>per capita </it>income, those classified as having black skin color and those with dental treatment needs had higher dental pain prevalence than their counterparts. Students from areas with low Human Development Index had higher prevalence of dental pain than those from the more developed areas regardless of individual characteristics.</p

An investigation of psychological, social and environmental correlates of obesity and weight gain in young women

Objectives: This study explored the biological, psychological, social and environmental correlates of young women\u27s current weight and retrospective 2-year weight change. Methods: A total of 790 young women (mean age 26.8 years), sampled from the Australian Longitudinal Study on Women\u27s Health, provided self-reported data on their height and weight, sociodemographics and a range of biological, psychological, social and environmental variables. Results: Several variables from all domains (biological, psychological, social support and environmental) were correlated with higher body mass index, and less strongly greater 2-year weight change. Key correlates included the tendency to never put on weight, no matter what; self-efficacy for avoiding weight gain, and for healthy eating; attention paid to weight; family support and friends\u27 support/sabotage of physical activity/healthy eating; and perceived difficulty of taking the stairs rather than the elevator as part of the daily routine. Conclusions: Intervention strategies aimed at reducing weight gain and obesity may need to focus on social and environmental, as well as psychological factors; however, further research is necessary to confirm these findings given that a number of hypothesized associations were not observed.<br /

Psychometric properties and the prevalence, intensity and causes of oral impacts on daily performance (OIDP) in a population of older Tanzanians

BACKGROUND: The objective was to study whether a Kiswahili version of the OIDP (Oral Impacts on Daily Performance) inventory was valid and reliable for use in a population of older adults in urban and rural areas of Tanzania; and to assess the area specific prevalence, intensity and perceived causes of OIDP. METHOD: A cross-sectional survey was conducted in Pwani region and in Dar es Salaam in 2004/2005. A two-stage stratified cluster sample design was utilized. Information became available for 511 urban and 520 rural subjects (mean age 62.9 years) who were interviewed and participated in a full mouth clinical examination in their own homes. RESULTS: The Kiswahili version of the weighted OIDP inventory preserved the overall concept of the original English version. Cronbach's alpha was 0.83 and 0.90 in urban and rural areas, respectively, and the OIDP inventory varied systematically in the expected direction with self-reported oral health measures. The respective prevalence of oral impacts was 51.2% and 62.1% in urban and rural areas. Problems with eating was the performance reported most frequently (42.5% in urban, 55.1% in rural) followed by cleaning teeth (18.2% in urban, 30.6% in rural). More than half of the urban and rural residents with impacts had very little, little and moderate impact intensity. The most frequently reported causes of impacts were toothache and loose teeth. CONCLUSION: The Kiswahili OIDP inventory had acceptable psychometric properties among non-institutionalized adults 50 years and above in Tanzania. The impacts affecting their performances were relatively common but not very severe

Prevalence and correlates of self-reported state of teeth among schoolchildren in Kerala, India

BACKGROUND: Oral health status in India is traditionally evaluated using clinical indices. There is growing interest to know how subjective measures relate to outcomes of oral health. The aims of the study were to assess the prevalence and correlates of self-reported state of teeth in 12-year-old schoolchildren in Kerala, India. METHODS: Cross-sectional survey data were used. The sample consisted of 838 12-year-old schoolchildren. Data was collected using clinical examination and questionnaire. The clinical oral health status was recorded using Decayed, Missing and Filled Teeth (DMFT) and Oral Hygiene Index – Simplified (OHI-S). The questionnaire included questions on sociodemographics, self reports of behaviour, knowledge and oral problems and a single-item measuring self-reported state and satisfaction with appearance of teeth. The Kappa values for test-retest of the questionnaire ranged from 0.55 to 0.97. RESULTS: Twenty-three per cent of the schoolchildren reported the state of teeth as bad. Multivariate logistic regression showed significant associations between schoolchildren who reported to have bad teeth and poor school performance (Odds Ratio (OR) = 2.5), having bad breath (OR = 2.4), food impaction (OR = 1.7) dental visits (OR = 1.6), being dissatisfied with appearance of teeth (OR = 4.2) and caries experience (OR = 1.7). The explained variance was highest when the variables dental visits, bleeding gums, bad breath, food impaction and satisfaction with appearance were introduced into the model (19%). CONCLUSION: A quarter of 12-year-olds reported having bad teeth. The self-reported bad state of teeth was associated with poor school performance, having bad breath and food impaction, having visited a dentist, being dissatisfied with teeth appearance and having caries experience. Information from self-reports of children might help in planning effective strategies to promote oral health

Prevalence of Helicobacter pylori infection and associated factors among adults in Southern Brazil: a population-based cross-sectional study

BACKGROUND: Helicobacter pylori (Hp) infection is associated with several upper gastrointestinal disorders. Local data on the epidemiology of the infection are scarce in Brazil. The purpose of this study is to measure the prevalence rate and to explore the associated factors among the adult population living in Pelotas, a southern Brazilin city. METHODS: This was a population-based cross-sectional study. Through a multi-stage sampling method all individuals 20 years and over living at the selected households at the urban area of the city were interviewed regarding past and current socio-economic indicators; demographic characteristics; nutritional and behavioural habits; and history of upper gastrointestinal symptoms.Hp infection was ascertained through the (13)C-UBT. Due to the high prevalence, data were analysed through robust Poisson regression. All analyses took into account the family clustering of the data. RESULTS: Among 563 eligible individuals, 363 agreed to perform the (13)C-UBT (refusal rate of 35.5%). Refusals were associated with female sex, consumption of mate drinking, and presence of upper gastrointestinal symptoms. The prevalence rate of H. pylori infection was 63.4% (95%CI 59.3%–69.3%). In crude analyses, prevalence was associated with increasing age, non-white skin colour, lower current family income, lower education level, higher size of the family, low socio-economic conditions in childhood, higher number of siblings and attendance to day-care centres in childhood, and presence of dyspeptic symptoms. In adjusted analysis the level of education of the father was inversely associated with the infection, whereas number of siblings and attendance to day-care centre in childhood were directly associated with it. Non-white skin colour remained significantly associated with increased prevalence even after allowing for past and current socio-economic characteristics, age and sex. Compared to non-symptomatic individuals, those reporting dyspeptic symptoms presented a higher prevalence of the infection even after allowing for current and past socio-economic conditions, ethnicity, age, and sex. CONCLUSION: Hp infection is as common among adults in southern Brazil as it is in other developing countries. Socio-economic conditions in childhood besides ethnicity and presence of dyspeptic symptoms were the factors significantly associated with the infection

Affinity Inequality among Serum Antibodies That Originate in Lymphoid Germinal Centers

Upon natural infection with pathogens or vaccination, antibodies are produced by a process called affinity maturation. As affinity maturation ensues, average affinity values between an antibody and ligand increase with time. Purified antibodies isolated from serum are invariably heterogeneous with respect to their affinity for the ligands they bind, whether macromolecular antigens or haptens (low molecular weight approximations of epitopes on antigens). However, less is known about how the extent of this heterogeneity evolves with time during affinity maturation. To shed light on this issue, we have taken advantage of previously published data from Eisen and Siskind (1964). Using the ratio of the strongest to the weakest binding subsets as a metric of heterogeneity (or affinity inequality), we analyzed antibodies isolated from individual serum samples. The ratios were initially as high as 50-fold, and decreased over a few weeks after a single injection of small antigen doses to around unity. This decrease in the effective heterogeneity of antibody affinities with time is consistent with Darwinian evolution in the strong selection limit. By contrast, neither the average affinity nor the heterogeneity evolves much with time for high doses of antigen, as competition between clones of the same affinity is minimal.Ragon Institute of MGH, MIT and HarvardSamsung Scholarship FoundationNational Science Foundation (U.S.). Graduate Research Fellowship (Grant 1122374